Lab 1 – Measurements of Frequency - Astro Pas Rochester

Physics of Music PHY103 Lab Manual
¼’’ phone (TRS) connector
(male)
PURPOSE
The purpose of this lab is to gain familiarity with varying electronic signals and connect detection
of sound waves to the equipment that we use to measure them. We will gain a working knowledge of a
function generator, an oscilloscope, and a counter/timer. We will look at signals picked up by an
oscilloscope probe and that from a microphone. We will experiment with different ways of measuring
frequency. The goal of the lab report is to compare and contrast our different measuring frequency
measuring techniques.
PROCEDURE
Part I – The Function Generator
• Turn on the function generator.
• Press in the button on the front panel with the sine wave picture.
• Where it is labeled “Range,” press the “500” button.
• Use the “Course” and “Fine” tuning dials (where it is labeled “Frequency” on the front panel) until
the display reads 300 Hz.
• In your notebook, write “300 Hz” for the value you obtained for your frequency using the function
generator on your first trial. You will want to record your different measurements!
• Turn the Output level (amplitude) knob on the function generator so the output is at about half of
the maximum (this is so it won’t make a very loud sound in the next step).
• Connect the output of the function generator to the speaker. Adjust the amplitude. Vary the
frequency from the function generator. Make sure you can hear a tone from the speaker. Get a
feeling for what frequencies correspond to which sounds.
• Explore the range of your hearing in frequency. What is the lowest frequency you can hear and
the highest you can hear?
• Change the signal to a square wave or a triangle wave. Notice that they have different sounds.
• Revert to sine wave, set the frequency back to 300Hz and disconnect the speaker.
Please keep the speaker away from the oscilloscope to prevent damage to the CRT
screens!
Part II – The Oscilloscope (you will be using Tenma scopes)
1. Turn on the oscilloscope by pushing in the power. It will take a few seconds for a trace to appear
on the screen. If one does not appear in a few seconds, try increasing the trace intensity (see #3).
2. Connect the output of the function generator to one of the inputs of the oscilloscope.
3. Adjust the intensity. This is done by turning the intensity button on the Tenma scopes in the
Display section.
4. There is a FOCUS knob. You can adjust this knob to focus the line in the CRT monitor.
5. Note that if the speaker is near the oscilloscope, its magnet can distort the display. This is kind of
fun to show but if you do too much of this it can damage the CRT and permanently warp it (we
had this happen one year.)
6. There is a MODE switch in the “Vertical” section. If your signal from the function generator is
going into Channel 1 then move this switch to “CH 1.” This allows you to look at channel 1.
There are two channels available so that it is possible to compare two traces at once. To show
both traces at once (that is the signals going into channel 1 and 2), select the DUAL mode.
Ordinarily you look channel 1 or 2 in the y axis vs time in the x axis.. The X-Y mode allows you
to look at an x versus y display. The horizontal (x-axis) signal is connected through the CH1 X